1. Field of the Invention
This invention relates to a microfiche carrier provided in a microfiche projection apparatus such as a microfiche reader or a microfiche reader-printer.
2. Description of the Prior Art
A microfiche carrier is a microfiche holding and moving apparatus for moving a microfiche crosswise relative to a projection optical portion to cause a desired image frame of a number of image frames in which images are regularly recorded in the form of a matrix on the surface of the microfiche to be retrieved and positioned at the projection optical portion.
Various types or structures have been proposed for the microfiche carrier, but the type in which plates for sandwiching a microfiche therebetween are movable is most popular. The microfiche carrier of this type has two upper and lower transparent plates for sandwiching a microfiche therebetween and holding it flatly, and a transparent plate moving mechanism for supporting the two upper and lower transparent plates sandwiching the microfiche therebetween and moving the two transparent plates relative to a projection optical portion.
The lower transparent plate is substantilly horizontally supported by the transparent plate moving mechanism, and the upper transparent plate is openable and closable relative to the lower transparent plate, and by the opening and closing thereof, placement of a microfiche onto a predetermined reference position on the lower transparent plate, insertion of the microfiche between the two transparent plates and removal of the used microfiche are accomplished. The opening and closing of the upper transparent plate is either manually effected or automatically effected in response to the movement of the transparent plates to a predetermined position by the moving mechanism.
The retrieving of a desired image frame of the microfiche sandwiched between the upper and lower transparent plates to the projection optical portion is accomplished either by manually operating the transparent plate moving mechanism or by automatic movement control. The manually operated type is such that the transparent plate moving mechanism is manually operated so that the index mark of the transparent plate moving mechanism is adjusted to a coordinates position corresponding to a desired image frame address of an index plate (a frame arrangement coordinates plate) disposed in place on the side of the apparatus body such as a reader, whereby the desired image frame portion is retrieved at a position corresponding to the projection optical portion. The automatic type is such that the address (or number) of a desired image frame is designated and input to a control circuit, whereby the transparent plate moving mechanism is automatically controlled in accordance with the input address and the desired image frame portion of the microfiche is retrieved at a position corresponding to the projection optical portion.
In any of the microfiche carrier of the manual retrieving type and the microfiche carrier of the automatic retrieving type as described above, for accurate retrieving of a desired image frame, it is important to accurately position and place a microfiche in advance at a predetermined reference position relative to the lower transparent plate and hold down the positioned and placed microfiche as it is by means of the upper transparent plate.
If the microfiche is set between the upper and lower transparent plates while positionally deviating from the predetermined reference position, in the case of the manual retrieving type, accurate retrieving of a desired image frame cannot be accomplished because of its corresponding deviation from the index plate. Again in the case of the automatic retrieving type, accurate retrieving of a desired image frame cannot be accomplished because of its corresponding deviation from the amount of automatic drive control of the transparent plate moving mechanism based on the input address of the desired image frame.
The microfiche is a film in the form of a thin, light sheet and therefore, even if it is accurately positioned and placed at the predetermined reference position on the lower transparent plate, when the hand or fingers are released from the microfiche, the microfiche is liable to slide naturally and readily on the lower transparent plate and thus is liable to positionally deviate from the predetermined reference position. Particularly, when the lower transparent plate and the microfiche placed thereon are not in intimate contact and an air layer is present therebetween with the underside of the microfiche floating from the surface of the lower transparent plate or when the projection apparatus is installed in an inclined posture and therefore the lower transparent plate is inclined beyond a certain degree, the above-described sliding and positional deviation of the placed microfiche is liable to occur. Also, a shock or wind pressure occurring when the upper transparent plate is closed relative to the lower transparent plate may readily result in the above-described sliding and positional deviation of the placed microfiche. Accordingly, it has actually been very difficult and often cumbersome to accurately position the microfiche between the upper and lower transparent plate without any positional deviation from the predetermined reference position and set the microfiche in its sandwiched position.
So, for example, it has been proposed to provide on the lower transparent plate side a plate spring member for holding down the leading end edge of a microfiche and hold down the leading end edge of the microfiche relative to the surface of the lower transparent plate by the plate spring, thereby preventing the sliding and positional deviation of the microfiche placed on the lower transparent plate from the predetermined reference position. However, this is liable to injure the leading end edge of the microfiche by the insertion or removal thereof between the holding-down plate spring and the lower transparent plate.